Visual guidance using ultrasound images has been successfully used for inserting core biopsy needles into tissue to procure tissue samples from a living body, resulting in high rates of sensitivity of tissue diagnosis. Accurate positioning of a biopsy needle by ultrasound guidance can be facilitated by providing a set of numerical positioning data for the biopsy needle such as an insertion length of the needle to reach an object from a skin and an insertion angle between a longitudinal axis of the needle and a horizontal axis of an ultrasound transducer visualizing the tissue object. An insertion angle and a length of a biopsy needle to reach a tissue object could be calculated by a trigonometric measurement using a measured vertical depth from a point of a contact portion of a transducer placed on a skin to a ultrasonographically visualized tissue object and a horizontal distance from the point of the contact portion of the transducer to a rotation center of the biopsy needle.
Although assisted by ultrasonographic visualization of a tissue object, it sometimes would be technically challenging to accurately place a transducer over the tissue object and to align a point of a contact portion of the transducer substantially tangentially with a center of the tissue object. In a situation where there are a range of varying positions of a center of a small tissue object in a living body, for example, during respirations or involuntary body movements, there would be an increase in error in estimating both the insertion angle and length of the needle to reach the tissue object. These inaccuracies may be minimized if a point of a contact portion of a transducer and a center of a tissue object is ultrasonographically visualized, if the point of the contact portion of the transducer is movably adjustable in an ultrasonographic field to get linearly aligned with the center of the tissue object and if an insertion angle of a biopsy needle is rotationally adjustable at a range of ratios to positional changes of the point of the contact portion of the transducer in the ultrasonographic field in a way changes in a position of the point of the contact portion of the transducer in relation to the center of the tissue object predictably result in changes in an insertion angle of the needle toward the center of the tissue object and vice versa.